I asked support, and they pointed as WIFI as the cause of the problem.
I thought it was strange as my router was reporting a decent signal strength of -75db… in line with the average of my wifi router.
But then I noticed that the TX and RX rates were very different, 40M vs 5M, kind of.
So I replaced the PBC antenna with an external one with magnetic base. I tried different locations until the signal streng improved to -59DB.
Now I can see that TX and RX rates are more similar (70M vs 50M and the like).
I have sent a decent size print and worked fist time, which seems like a step in the right direction.
However I left UP Studio monitoring the print, time left, etc, and the connection drops from time to time, but I also feel like the “load” of the printer makes wifi more unstable: printing, pinging the device, etc. Seems to make the connection drops more likely.
I going to wire up a spare router antenna (some parts still on order…), and test this out.
The printer has no problems maintaining a wired connection when the printer is busy ?
Perhaps a wireless connection requires more brain power.